1. Field of the Invention
The present invention relates to an image display method of displaying images obtained by radiography and so on, and to an image display apparatus using the same.
2. Description of a Related Art
Photography using radiations (X-rays, xcex1-rays, xcex2-rays, xcex3-rays, electron rays, ultraviolet rays and so on) has hitherto been used in a variety of fields, and especially in the medical field it becomes one of indispensable measures for diagnoses. X-ray radiography has had a lot of improvements since its first realization and now combining fluorescent screen and X-ray film is the mainstream. On the other hand, with various digitalized apparatuses such as X-ray CT, ultrasonic diagnosis, MRI and so on realized in recent years, diagnostic information processing systems are being structured in hospitals. With a lot of researches conducted to digitize X-ray images, radiography using photostimulable phosphor has been established and put into practical use to replace X-ray radiography.
Photostimulable phosphor (accumulative phosphor) is such a substance as follows. That is, the substance accumulates a part of the radiation energy when radiation is irradiated. After that, when excitation light such as visible light and so on is irradiated, the substance radiates photostimulated luminescence light in accordance with the accumulated energy. Existence of photostimulable phosphor has been known so far. The radiography using photostimulable phosphor is as follows. That is, a radiation image of an object like a human body is photographed and recorded on a sheet coated with photostimulable phosphor. Since photostimulated luminescence light is produced when the photostimulable phosphor sheet is scanned by excitation light such as a laser beam and so on, image data can be obtained by reading the light photo-electrically. After proper processing of the image data, a radiation image can be shown as a visible image on a display such as a CRT or on a film printed by a laser printer and so on.
The radiography compares with the conventional X-ray radiography in photographic sensibility and image quality. For example, compared with the conventional X-ray radiography, an exposure area is exceedingly wide and a response of photostimulated luminescence light is almost in proportion to an exposure amount in all the exposure area. Therefore, even if an object is photographed by any amount of radiation, image signals having proper gradation can be obtained by finding the luminous area of the image and normalizing it. Also with a proper process of image signals obtained by this way, the image having good quality can be produced under a variety of photographing condition. Moreover, it is possible to store a lot of image data set for a long time without deterioration of image quality because the image by this radiophotography can be stored as digitized data. Such a system storing images as image data sets will be useful to the development of medical diagnostic information system.
In medical diagnosis using a display such as a CRT and so on, a plurality of images are often displayed successively. In this case, a new image is displayed over an image previously shown or a new image is displayed after the previous one is eliminated. However, when the new image is displayed over the previous one, it is difficult to know where the previous image ends and where the new one starts because the two images are displayed on the same screen. Thus, there is a fear that the two images might be confused.
Japanese Patent No. 2976196 discloses a radiation image information reading and displaying apparatus which reads radiation images to obtain image data, successively displays images on the basis of those image data, and eliminates existing images previous to displaying images in accordance with reading the images.
In the above apparatus, it does not occur that a previous image and a next image are confused because only one image is displayed on one screen. However, in medical diagnosis, both the previous and next images are often observed as a series of images. For example, when the same part of a human body is photographed from different angles or at different times, it becomes difficult to realize the connection of the series of images if the previous one is eliminated.
The present invention was accomplished in view of such problems. An object of the present invention is to provide an image display method wherein, in the process of receiving and successively displaying a plurality of image data representing a plurality of pictures in order, a previously displayed image can be distinguished from a next image to be displayed easily and the outline of the previously displayed image can be grasped. Also, another object of the present invention is to provide an image display apparatus using the method.
In order to achieve the above object, an image display method according to the present invention comprises the steps of: (a) setting gradation processing condition of first image data representing a first picture; (b) executing gradation processing of the first image data in accordance with the gradation processing condition set at step (a); (c) displaying the first picture by using the first image data obtained at step (b); (d) altering the gradation processing condition set at step (a) when reception of second image data representing a second picture starts; (e) executing gradation processing of the first image data in accordance with the gradation processing condition altered at step (d); (f) receiving second image data representing a second picture in sequence; (g) generating overwritten image data at predetermined intervals by replacing a part of the first image data obtained at step (e) with a part of the second image data received at step (f); (h) setting gradation processing condition of the overwritten image data generated at step (g); (i) executing gradation processing of the overwritten image data in accordance with the gradation processing condition set at step (h); and (j) displaying an overwritten picture by using the overwritten image data obtained at step (i).
An image display apparatus according to the present invention comprises: first means for receiving a plurality of image data representing a plurality of pictures in sequence; second means for generating overwritten image data at predetermined intervals by replacing a part of first image data representing a first picture with a part of second image data representing a second picture; third means for altering gradation processing condition of the first image data representing the first picture being previously displayed, and thereafter setting gradation processing condition of the overwritten image data generated by the second means; fourth means for executing gradation processing of the first image data in accordance with the gradation processing condition altered by the third means, and thereafter executing gradation processing of the overwritten image data generated by the second means in accordance with the gradation processing condition set by the third means; and fifth means for displaying the first picture by using the first image data obtained by the fourth means, and thereafter displaying an overwritten picture by using the overwritten image data obtained by the fourth means.
According to the present invention, a new image is successively received and displayed after changing the gradation of a previously displayed one, so that the previous image and the new image are confused by no means and the outline of the previous image can be grasped.